SQL error on Postgress

I am getting an PGError when using the following code snippet to search for all records that have an expirationDate greater than today.

campaigns = Table(:users)
campaigns.where(campaigns[:expirationDate].gt(Date.today.midnight))

According to this error it looks like the '*' is missing between the select and from.

ActionView::Template::Error (PGError: ERROR: syntax error at or near "FROM"
LINE 1: SELECT FROM "users" WHERE "users"."expiration...

                ^

: SELECT FROM "users" WHERE "users"."expirationDate" > '2010-04-22 06:00:00.000000')